The capacity of removable record carriers increases continuously. At the same time, the manufacturing costs of a record carrier hardly increase or sometimes even decrease. Currently, DVD-based record carriers are a major way of distributing audio/video content. A dual-layer DVD can store 9.4 GBytes of digital content. Future removable record carriers, such as Blu-ray discs (BD), can store even more content. The costs of pre-recorded record carriers is thus increasingly determined by the content. Much effort has been spent on protecting the content, typically by using copy protection mechanisms based on cryptography. To decrypt the content, the reader needs to retrieve a decryption key. For DVD, a special identifier area on the disc, referred to as the Burst Cutting Area (BCA), has been defined on which additional information such as a serial number identifying the disc may be written. This number can be used to retrieve a decryption key. The disc is produced in a conventional mass-manufacturing process producing discs with the same pre-recorded content. In this process, also the BCA is produced, but not yet written to. In a separate process step, the identifier is written into the BCA, allowing for distinct codes to be written in the area.
Manufacturing costs of the disc are the same or very similar, irrespective of the amount of pre-recorded content. Increasingly, the capacity of the disc is getting so high that it may not be fully utilized or, if it were fully utilized, the content costs would make the disc prohibitively expensive.